I noticed that redstone dust dots on an upper elevation remain as a dot when connected to a lower line of redstone dust. Also, placing the dust on the top after breaking the dust on the top will make a line.
Demonstration:
Environment
OS Name Microsoft Windows 10 Pro
Version 10.0.16299 Build 16299
Java Version 8 Update 171 (build 1.8.0_171-b11)
pre6 or pre7?